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> Did mushrooms evolve to be poisonous because that's advantageous
> somehow? Or do they just happen to be poisonous to animals because of
> their unusual chemistry?
Both.
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triple_r wrote:
> Invisible <voi### [at] dev null> wrote:
>> Why do overhead cables never flap around in the wind?
>
> They do, so of course they're designed to minimize that. Tension will increase
> the natural frequency of the cable, hopefully well above the vortex shedding
> frequency.
Vortex shedding frequency?
WIN!
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Darren New wrote:
>> Come to think of it, why doesn't rain short out power cables?
>
> Because power system engineers aren't stupid enough to put them close
> enough together a raindrop will bridge them.
I was thinking more of when everything has been covered in a continuous
layer of water...
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>> Why do some people like the X-Files?
>
> Because it's cool. The whole UFO "I want to believe" mantra as well as
> the "Trust no one" conspiracionist theories were all around in the 90s...
I just don't see the point.
Each episode, something happens which makes absolutely no sense. It's
not that it's "mysterious", it's just nonsensical. Molder and Scully
investigate. A series of utterly incomprehensible events occur. It turns
out that the conspiracy was actually a conspiracy to create a conspiracy
that would make people think the conspiracy was actually a conspiracy
about a conspiracy to create a conspiracy. But then that turns out to be
wrong too. And after about an hour of abject failure to make any kind of
weakly comprehendable sense, the show ends.
WTF?
I mean, seriously. Any moron can write a bunch of gibberish that doesn't
make sense. But where's the entertainment in that?!
>> Are mushrooms poisonous on purpose, or by accident?
>
> On purpose. They know you'd eat them otherwise.
I see...
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Invisible wrote:
>
> I was thinking more of when everything has been covered in a continuous
> layer of water...
How pure the rainwater even is? Pure water (H2O) doesn't lead
electricity (at least not very well), the usual water you get from tap
ain't pure, it has all kinds of particels within it, including metal
ones. I'd *guess* the rainwater hasn't got as much metal particels as
the water already on the ground and doesn't lead electricity as well.
Anyway, the smart people have calculated that the space between electric
wires is enough, even on hard storms. :-)
-Aero
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Eero Ahonen wrote:
> How pure the rainwater even is?
Depends on the local pollution levels. (Ever hear of acid rain?)
> Pure water (H2O) doesn't lead electricity (at least not very well)
In our lab, we measure water purity by electrical conductivity. The
higher the resistence, the purer the water...
...which is kinda silly really, given that the impurities that affect
resistence are the least relevant to the work we do.
> the usual water you get from tap
> ain't pure, it has all kinds of particels within it, including metal
> ones. I'd *guess* the rainwater hasn't got as much metal particels as
> the water already on the ground and doesn't lead electricity as well.
I would suggest that the ionic compounds disolved in tap water have a
*much* more significant effect than any hypothetical "metal particles"
it may contain...
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scott <sco### [at] scottcom> wrote:
> > Come to think of it, why doesn't rain short out power cables?
> Because air with rain in it is still an insulator?
Ok, there's definitely something here I'm seriously not understanding.
What does rain or water have *anything* to do shorting out power cables?
I don't get it.
Heck, there are power cables at the bottom of the sea. So what? What does
that have to do with anything?
It feels like everybody is writing like power cables were bare metal wires
with nothing covering them. Why?
--
- Warp
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> I was thinking more of when everything has been covered in a continuous
> layer of water...
Are you sure that every part between the pylon structure and the cable can
get wet to form a continuous path? It seems to me like part of the design
of the insulator is to keep other parts dry:
http://en.wikivisual.com/images/3/33/Pylon.detail.arp.750pix.jpg
Even if it does *all* get wet, it's going to be a really thin layer of
water, and even non-pure water is not a particularly good conductor, if you
do the math the resistance probably comes out pretty huge.
BTW, that photo also shows the dampers attached on the cables either side of
the fixing point.
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On Thu, 03 Sep 2009 09:14:41 +0100, Invisible <voi### [at] devnull> wrote:
>Rain water isn't chemically pure. (Depending on pollution levels.) Once
>the pylon gets wet, it's entire surface is covered in a continuous sheet
>of water, which also covers all of the cables. So why don't they short out?
There are insulators between the cables and pylons so there is no path for the
electricity to flow there. The conductors are spaced far enough apart so that
the electricity cannot jump between them. This is called engineering. ;)
--
Regards
Stephen
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Invisible <voi### [at] devnull> wrote:
> I mean, seriously. Any moron can write a bunch of gibberish that doesn't
> make sense. But where's the entertainment in that?!
I don't think everybody can write scripts of that quality. It requires
expertise and talent.
And some people like fiction for entertainment. If you don't like it,
that doesn't mean nobody else souldn't like it either.
--
- Warp
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